Fix -Wwritable-strings warnings in kasko code.

Should fix 32-bit clang/win builds after
https://codereview.chromium.org/405123002/

BUG=82385
TBR=hans

Review-Url: https://codereview.chromium.org/2018543002
Cr-Commit-Position: refs/heads/master@{#396187}
1 file changed